CA1139574A - Single air conduit refrigerated display case having ambient air defrost - Google Patents
Single air conduit refrigerated display case having ambient air defrostInfo
- Publication number
- CA1139574A CA1139574A CA000367125A CA367125A CA1139574A CA 1139574 A CA1139574 A CA 1139574A CA 000367125 A CA000367125 A CA 000367125A CA 367125 A CA367125 A CA 367125A CA 1139574 A CA1139574 A CA 1139574A
- Authority
- CA
- Canada
- Prior art keywords
- air
- during
- display case
- conduit
- opening
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
- F25D21/06—Removing frost
- F25D21/12—Removing frost by hot-fluid circulating system separate from the refrigerant system
- F25D21/125—Removing frost by hot-fluid circulating system separate from the refrigerant system the hot fluid being ambient air
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47F—SPECIAL FURNITURE, FITTINGS, OR ACCESSORIES FOR SHOPS, STOREHOUSES, BARS, RESTAURANTS OR THE LIKE; PAYING COUNTERS
- A47F3/00—Show cases or show cabinets
- A47F3/04—Show cases or show cabinets air-conditioned, refrigerated
- A47F3/0439—Cases or cabinets of the open type
- A47F3/0443—Cases or cabinets of the open type with forced air circulation
- A47F3/0447—Cases or cabinets of the open type with forced air circulation with air curtains
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D2317/00—Details or arrangements for circulating cooling fluids; Details or arrangements for circulating gas, e.g. air, within refrigerated spaces, not provided for in other groups of this subclass
- F25D2317/06—Details or arrangements for circulating cooling fluids; Details or arrangements for circulating gas, e.g. air, within refrigerated spaces, not provided for in other groups of this subclass with forced air circulation
- F25D2317/068—Details or arrangements for circulating cooling fluids; Details or arrangements for circulating gas, e.g. air, within refrigerated spaces, not provided for in other groups of this subclass with forced air circulation characterised by the fans
- F25D2317/0684—Details or arrangements for circulating cooling fluids; Details or arrangements for circulating gas, e.g. air, within refrigerated spaces, not provided for in other groups of this subclass with forced air circulation characterised by the fans the fans allowing rotation in reverse direction
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Defrosting Systems (AREA)
- Freezers Or Refrigerated Showcases (AREA)
- Cold Air Circulating Systems And Constructional Details In Refrigerators (AREA)
Abstract
SINGLE AIR CONDUIT REFRIGERATED DISPLAY CASE
HAVING AMBIENT AIR DEFROST
ABSTRACT OF THE DISCLOSURE
A single air conduit refrigerated display case having an ambient air automatic defrost system and a method of operating such a case. The display case has an access opening in one wall for enabling products within the display section to be removed. The access opening can be either in the top or front wall of the display case. The single air conduit extends in an approximately U-shaped formation around the display case. The air conduit has openings at both ends, with such openings being located on opposite sides of the access opening. Arranged within the air conduit is at least one reversible fan and a set of refrigeration coils.
During a refrigeration cycle the fan circulates air through the air conduit in a first direction towards the refrigeration coils. When frost buildup within the display case has reached a certain level, the system is switched to a defrost cycle.
During the defrost cycle, the fan circulates the air in the opposite direction through the air conduit and draws in ambient air from outside of the display case. Since such ambient air is of a higher temperature than the normally refrigerated air, it serves to defrost the system. The ambient air, after passing over the evaporator coils and through the air conduit, is expelled from the air conduit in a direction towards the outer side of the refrigerated case so as to move away from the interior of the case.
HAVING AMBIENT AIR DEFROST
ABSTRACT OF THE DISCLOSURE
A single air conduit refrigerated display case having an ambient air automatic defrost system and a method of operating such a case. The display case has an access opening in one wall for enabling products within the display section to be removed. The access opening can be either in the top or front wall of the display case. The single air conduit extends in an approximately U-shaped formation around the display case. The air conduit has openings at both ends, with such openings being located on opposite sides of the access opening. Arranged within the air conduit is at least one reversible fan and a set of refrigeration coils.
During a refrigeration cycle the fan circulates air through the air conduit in a first direction towards the refrigeration coils. When frost buildup within the display case has reached a certain level, the system is switched to a defrost cycle.
During the defrost cycle, the fan circulates the air in the opposite direction through the air conduit and draws in ambient air from outside of the display case. Since such ambient air is of a higher temperature than the normally refrigerated air, it serves to defrost the system. The ambient air, after passing over the evaporator coils and through the air conduit, is expelled from the air conduit in a direction towards the outer side of the refrigerated case so as to move away from the interior of the case.
Description
BACKGROUND OF TEIE INV~NTION
The present invention relates to single air condult refrigerated display cases having an ambient air defrost sytem.
Of primary concern are display cases having access openings in their front walls. Both within the specification and the claims of the present application, all references to refrigeration apparatus or refrigeration operations are intended to include cooling both at a temperature below 32F, such as associated with frozen food display cases, and in excess of 32F, such as typically associated with dair~ food and fresh meat display cases.
Refrigerated display cases having only a single air conduit with both front and top access openings have been used for many years. Such open front cases are conventionally utilized for displaying dairy and meat productsO
In the operation of all types of refrigerated display cases, it is desirable to include a system capable of automatically defrosting the display case. The defrost cycle can be actuated either at set periodic times or when the frost buildup within the system has reached a certain predetermined level. Such systems are typically thermostat-ically controlled so as to switch from a refrigeration cycle
The present invention relates to single air condult refrigerated display cases having an ambient air defrost sytem.
Of primary concern are display cases having access openings in their front walls. Both within the specification and the claims of the present application, all references to refrigeration apparatus or refrigeration operations are intended to include cooling both at a temperature below 32F, such as associated with frozen food display cases, and in excess of 32F, such as typically associated with dair~ food and fresh meat display cases.
Refrigerated display cases having only a single air conduit with both front and top access openings have been used for many years. Such open front cases are conventionally utilized for displaying dairy and meat productsO
In the operation of all types of refrigerated display cases, it is desirable to include a system capable of automatically defrosting the display case. The defrost cycle can be actuated either at set periodic times or when the frost buildup within the system has reached a certain predetermined level. Such systems are typically thermostat-ically controlled so as to switch from a refrigeration cycle
- 2 -.
7~i to a defrost cycle of operation. By this manner of operation, it is possible to avoid any significant frost buildup within the display case.
Typically within the prior art, there have been three different approaches employed for defrosting refriger-ated display cases. The Eirst approach involves the use of electric resistance heaters that are arranged adjacent to the refrigeration coils of the refrigeration mechanism. During a defrost cycle, these heaters supply heat in an effort to ` 10 melt the frost buildup on the coils but also adds warmer air to the air conduit for circulation within the case. The particular technique is relatively simple both in its construc-tion and operation. However, since the electrical heaters are high voltage heaters that utilize significant electricity during operation, with the rapidly increasing cost of electric-ity it has become extremely uneconomical to employ such systems.
Furthermore, the warm air circulated in the case can raise the temperature of the case too high. Thus, attempts have been made to find other alternatives to such a system.
A second type of system circulates hot compressed - gaseous refrigerant through the refrigeration coils during the defrost cycle. During the defrost ~cycle, a valve control mechanism shuts off the supply of refrigerant to the refrigera-: tion coils and alternatively feeds superheated compressed gaseous refrigerant through the coils. This hot gas serves ~; to melt any frost buildup that has occurred on the refrigera-: tion coils but simultaneously provides heat within the air conduit which can be circulated through the display case, which again is disadvantageous. While this type of system ~ 3~ ~t~ -does not suffer from the high cos-t of opera-tion of the electrical heater defrost system, the heated gas sys-tem involves a relatively high construction cost. Due to the requirement that the system be able to selec-tively switch between the supply of heated gas and refrigerant to the refrigeration coils, a complicated valving structure must - be provided. Such a mechanism significantly increases the cost of construction of the display case. In addition, the provision of such a complicated system only increases - 10 the number of complex parts capable of breaking down and necessitating costly repairs.
The third type of system employed for defrosting display cases relles upon ambient air. It is this general category with which the invention of the present application is concerned. One type of system that employs ambient air during the defrost cyle is exemplified by those embodiments illustrated in U.S. Patent Nos. 3,403,525, 3,850,003 and
7~i to a defrost cycle of operation. By this manner of operation, it is possible to avoid any significant frost buildup within the display case.
Typically within the prior art, there have been three different approaches employed for defrosting refriger-ated display cases. The Eirst approach involves the use of electric resistance heaters that are arranged adjacent to the refrigeration coils of the refrigeration mechanism. During a defrost cycle, these heaters supply heat in an effort to ` 10 melt the frost buildup on the coils but also adds warmer air to the air conduit for circulation within the case. The particular technique is relatively simple both in its construc-tion and operation. However, since the electrical heaters are high voltage heaters that utilize significant electricity during operation, with the rapidly increasing cost of electric-ity it has become extremely uneconomical to employ such systems.
Furthermore, the warm air circulated in the case can raise the temperature of the case too high. Thus, attempts have been made to find other alternatives to such a system.
A second type of system circulates hot compressed - gaseous refrigerant through the refrigeration coils during the defrost cycle. During the defrost ~cycle, a valve control mechanism shuts off the supply of refrigerant to the refrigera-: tion coils and alternatively feeds superheated compressed gaseous refrigerant through the coils. This hot gas serves ~; to melt any frost buildup that has occurred on the refrigera-: tion coils but simultaneously provides heat within the air conduit which can be circulated through the display case, which again is disadvantageous. While this type of system ~ 3~ ~t~ -does not suffer from the high cos-t of opera-tion of the electrical heater defrost system, the heated gas sys-tem involves a relatively high construction cost. Due to the requirement that the system be able to selec-tively switch between the supply of heated gas and refrigerant to the refrigeration coils, a complicated valving structure must - be provided. Such a mechanism significantly increases the cost of construction of the display case. In addition, the provision of such a complicated system only increases - 10 the number of complex parts capable of breaking down and necessitating costly repairs.
The third type of system employed for defrosting display cases relles upon ambient air. It is this general category with which the invention of the present application is concerned. One type of system that employs ambient air during the defrost cyle is exemplified by those embodiments illustrated in U.S. Patent Nos. 3,403,525, 3,850,003 and
3,937,033, all to Beckwith et al. Each of these systems uses fans separate from the main air circulating fans. These extra fans are turned on during the defrost cycle for pulling - ambient air from outside of the display case into the air conduits. A second type of system is illustrated in U.S.
Patent No. 3,082,612 to Beckwith, which system draws ambient air into the main circulation path through ports located in the lower front panel of the refrigerated display case. Such ports are normally closed during the refrigeration cycle and are opened during the defrosting-cycle. The Beckwith et al.
'003 patent indicates that the concepts described in patents Nos. 3,082,612 and 3,403,525 did not prove to be practical .:
and hence were not commercially feasible.
Finally, a third type of ambient air defros~ing system is shown in U.S. Pat~nt No. 4,144,720 to Subera et al., which is assigned to the same assignee as the present applica-tion. In the foregoing patent application, an open frontrefrigerated display case having primary and secondary air conduits is disclosed. In this system, reversible fans are employed for reversing the direction of flow of air within the conduits and simulataneously drawing in air from outside of the display case.
Another system employing reversible fans for ambient air defrost is shown in U.S. Patent No. 4,026,121. This patent, however, refers to short-circulating the air flow between the primary and secondary air bands for the purpose of supplying warmer air to the primary band.
It has been recognized that an ambient air defrost operation can be incorporated into an open top refrigerated display case as disclosed in U.S. Patent No. 4,120,174 to - Johnston. The Johnston patent illustrates an open top case having a single air conduit extending around the c;ase.
During the refrigeration cycle, the air flows in a first direction and during the defrost cycle the direction of the air flow is reverse with ambient air being drawn into the conduit. The quantity of air flow during the defrost cycle ~ ~is greater than during refrigeration. The defrost air, after passing through the conduit, is expelled in a direction up and over the refrigerated case. It has been found during the development of the present inventlon, that with a defrost .
S~
~3 air flow pa-ttern such as disclosed in the Johnston paten-t a significant portion of the expelled air will fall back towards the access opening in the refrigerated case and reenter the air conduit at the other side of the access opening.
Similar to the open top display case of the above-identified patent to Johnston, there also are open front single air conduit cases which employ the same air defrost techniques as disclosed by the Johnston patent. During the defrost operation of such air defrost cases, the volume of the reverse air flow is relatively high and significantly greater than the air flow flow during the refrigeration cycle.
Such a greater air flow is utilized so as to minimize the time needed for the defrost operation. As shown in Figure 1, which illustrates this type of prior art display case, the higher air volume flow causes the warmer defrost air to re-enter the display case which potentially can damage the products in the case. In addition the greater air flow causing the cold air to flow upwardly can result in hitting the customer in the face with such cold air.
r.
SU~M~RY OF T~E INVENTION
An object of the present invention is to provide an improved ambient air defrost system within a single air conduit open front refrigerated display case.
Another object of the present invention is to provide an energy efficient open front refrigerated display case employing an improved ambient air defrost system in which the ambient air is drawn into the air conduit by re-versing the direction of flow of air through the conduit.
f~
A further object of the present invention is to provide an open front refrigerated display case having a single air conduit and a reversible fan arranged within the conduit for propelling air in a forward direction through the refrigeration coils during a refrigeration cycle and circulating air in a reverse direction so as to draw in ambient air from outside of the case during a defrost cycle and to prevent the defrost air when expelled from the conduit from being drawn back into the refrigerated case.
A still further object of the present invention is to provide an improved procedure for defrosting an open front refrigerated display case by the use of ambient air.
These objectives are achieved by the utilization of a refrigerated display case with a front access opening that is constructed in accordance with the present invention.
The display case is providedwith an approximatel~ U-shaped air conduit that extends around the display case and has openings at its opposite ends at opposite sides of the access opening of the display case. Arranged within the air conduit are the refrigeration coils and at least one reversible fan.
- In larger display cases, it is often necessary to use either two or three fans spaced along the longitudinal axis of the _ case in order to generate a sufficient force for circulating the air; in such a system, however, each fan preferable would be a reversible fan and operate in the same manner as disclosed herein in accordance wi-th the present invention.
The reversible fan arranged within the U-shaped air conduit is capable of either circulating in a first direction towards the refrigeration coils during a refrigeration -~3~'7~
cycle or when the case is switched into a defrost cycle circulating the air in a second, opposite, direction. For the sa~e of convenience herein, the first direction shall be referred to as the forward direction and the second, opposite, direction as the reverse direction. The openings in the ends of the air conduit are aligned so that during the refrigeration cycle, refrigerated air leaves a first of the openings in a path towards the second opening so as to form an alr curtain across the access opening in the display case. This air travelling across ~he access opening in the display enters the second opening in the air conduit and is drawn along the conduit back towards the fan thereby establish-ing a continuous refrigerated air band. When the display case is switched into a defrost cycle, th~ refrigeration coils are deactivated and the direction of air flow is re-versed. The volume of the air flow during defrost is lower than the volume during refrigeration. During such reverse air flow, the air leaves the air conduit through the second opening. The air leaving the conduit is cooler than the ambient air since it has passed over the refrigeration coils for defrosting them; this expelIed defrost air being some-what cooled, therefore, is denser than the ambient air.
The dense defrost air being propelled at a lower volume and hence slower speed will fall to the floor as it leaves the air conduit. Hence the defrost air falls away from the display case; i.e., towards the outside of the display case, thereby preventing portions of the defrost air from reentering the case and travelling across the access opening in the case ~ ,r~
7'~
and being drawn back into the air condui-t. With such an air flow pattern, the defrost air also will not hit the customer in the face with cold air. The area of the second opening can be constructed to help direct the defrost air flow away from the display case. Consequently, during the reverse flow of air no air curtain is established and hence ambient air from outside of the case is drawn in through the first opening in the air conduit. Such ambient air being warmer than the refrigerated air serves to defrost the refrigeration coils.
It is advantageous to avoid having the defrost air flow reenter the display case and also reenter the air conduit. While the ambient air as it passes over the evapora-tor coils expels heat to the coils and the air drops in temperature, the temperature of such air is still warmer than the temperature to which the products are refrigerated.
If the defrost air reenters the conduit then this will significantly slow down the defrost operation. In addition, if the defrost air contacts the products it will raise the temperature of the products. By causing the defrost air to fall away from the refrigerated case, the products are protected without detrimentally increasing the defrost time perlod .
As frost accumulates-on the evaporator coils during the refrigeration cycle, the conduit becomes blocked. Hence when the defrost cycle is initiated the ~uantity of air flow will be substantially less than the air flow during the refrigeFation cycle. As the defrost cycle continues and the _g_ __ _. . . .. .. .. . . . ___ .__._. .. _ ... ~_~
~ 7L~
frost is eliminated, the defrost air flow will rise back toward the level of the re~rigeration air flow, although not surpassing it.
In order to eliminate the buildup of condensation and frost on the grill structures mounted at the openings at the ends of the air conduit, it may be desirable to pro-vide some type of mechanism for generating heat in these areas. For this purpose, within each of the areas, tubes containing the liquid refrigerant used in the system can be provided. These tubes are connected to the line that carries the liquid refrigerant for the refrigeration coils.
Since the liquid refrigerant is warmer than the refrigerated air, the tubes provide a limited quantity of heat within each of the openings. The quantity of heat, however, is sufficient to help eliminate the condensation and the re-sulting buildup of frost.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a sectional side elevational view of - an open front refrigerated display case in accordance with the prior art, when the display case is operated during a ; defrost cycle with the air flow being relatively high.
Figures 2 and 3 are sectional side elevational views of one embodiment of an open front refrigerated display case in accordance with the present invention, with Figure 2 showing the air flow pattern during refrigeration and Figure 3 showing the pattern during defrost.
Figures 4 and 5 are views similar to Figures 2 and 3 respectively of another embodiment of the present invention.
~3~
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An open front refrigeratecl display case 2 construc-t-ed in accordance with the present invention is illustrated in Figure 2. The display case has top, bottom, rear and side walls along with a partial front ~all. All of these walls are appropriately insulated. Front wall 4 has an access opening 6. Positioned above bottom wall 8 are a plurality of shelves 10, 12 and 14. The spacing between shelf 10 and bottom wall 8 is large enough to enable the fans and if desired the refrigeration coils, which are described later herein, to be arranged within that location. Extending along the top wall, rear wall and bottom wall is an air conduit 16. Arranged within air conduit 16 is at least one fan 18.
While only one fan is illustrated, typically for refrigerated cases that are eight feet long, two fans are employed and for cases twelve feet long there are three fans. The number of fans merely depends on the length of the case and the sige of the fans but have no bearing upon the scope of the present lnvention. All the fans arranged within air conduit 16 are reversible fans capable of being driven for propelling air in either direction.
ir conduit 16 has openings 20 and 22 at both of its ends at the top of the refrigerated display case. A
directional control grill 24 is mounted across opening 20.
Grill 24 is preferable constructed so as to assist in direct-ing air leaving a:ir conduit 16 through opening 20 towards opening 22 on the opposite side of access opening 6 of the display case. At the opposite side of the display case across opening 22 there is only positioned a cover plate having a plurali-ty of openings. The cover plate arxanged across opening 22 helpsto diffuse the air emitted during defrost. Such air directing grill structure and cover plate are generally known ln the prior art. In addition to help-ing in controlling the direction of Elow of the air enteringand leaving openings 20 and 22, the grill and cover plate also protect the openings from various debrls, such as trash, keys and coins.
Refrigeration coils 26 are positioned within air conduit 16 at a location either adjacent to or above fan 18, such as shown in the figures. In a conven~ional manner, when the display case is operated in a refrigeration cycle, the air passing through refrigeration coil 26 is cooled, or refrigera-ted. The extent to which air is cooled depends on the use to which the display case is to be put. If the display case is to serve for holding frozen food, then the air must be sufficiently cooled so as to maintain the interior of the case below 32F. If, however, the display case is used for storage of non-frozen products, such as 20~ dairy products, then a termperature slightly in excess of - 32F can be maintained. The term refrigeration, however, as used herein is intended to cover both types of system.
- Turning now to the structural arrangement in the area of opening 22, as shown in Figures 2 and 3, the inner surface 28 of the top part of the lower portion of front wall 4 is sloped in a direction towards the outside of dis-play case 2. This sloped construction of surface 28 helps to direct air leaving conduit 16 through opening 22 during ~ t7~
a defrost operation in a direction away from the display case as shown by the arrows in Figure 3.
During the refrigeration cycle of operation of the display case, air is circulated through air conduit 16 by fan 18 in a forward direction towards and through refrigeration coils 26, which are activated for cooling.
The volume of air flow during refrigeration is between 1000 and 1400 cfm. The air is cooled wllen passing through refrig-eration coils 26. The cooled air then travels through tlle remaining portion of conduit 16. As the air reaches opening 20 in conduit 16, it is forced out through grill 24 in a direction towards opening 22. In this manner, a curtain of cooled air is established across access opening 6 of the display case. The cooled air serves to refrigerate the lS products in the display case and also separate the warmer ambient air outside of the display case from the cooler air inside of the display case.
The air emitted through grill structure 24 and traveling across the access opening is received into open-ing 22 in the air conduit. This air is then drawn back intoair conduit 16 by a suction force established by fan 18.
Thus, during the refrigeration cycle a continuous band of cooled air is circulated by fan 18 through the display case.
The direction of travel of such air along the air band is illustrated in Figure 2.
Turning now to the defrost cycle, the air flow during this cycle of operation is illùstrated in Figure 3O
In any one of different conventional manners, the display case can be thermostatically or otherwise controlled so as -to switch between the refrigeration cycle and the defrost cycle. By one such technique, the switching can occur when a cer-tain degree of frost bui.ldup is detected on the refrig-eration coils. Another possible alternative is at set time intervals to switch the operation of the display case from a refrigeration cycle to a def.rost cycle.
During the defrost cycle, the operation of fan 18 is reversèd so as to propel air in a reverse direction away from refrigeration coils 26. When the fan is operated in this mode, air passes along conduit 16 out through open-ing 22. The air upon exiting from opening 22 is diffused and falls to the floor outside of the.case. In addition, the lower portion of wall 4 at its upper end has sloped inner surface 28. As the air leaving conduit 16 during the defrost cycle passes along sloped wall 25, the path of air curves into an arc directed up and away from display case 2.
Thus, in this mode of operation, there is no air curtain established across the access opening of display case 2 and also no continuous air band established through the display case. The volume of air flow during the.defrost operation is between 800 and 1100 cfm and should be less than the air flow during refrigeration. If the air flow during defrost is increased to above 1600 cfm then a curtain of air will be es-tablished across access opening 6 during the defrost 25: operation.
As air is propelled out of conduit 16 through opening 22, a partial vacuum is estabiished within the air conduit so as to cause air to be sucked into the conduit through opening 20. Since there is no air curtain in ,, " - ~
7,. ~
existence across the top of the display case during the de-frost cycle, the air sucked into the conduit through open-ing 20 is drawn from the ambient air surrounding the display case. Since such ambient air is of a higher temperature than the refrigerated air during the refrigeration cycle, such ambient air serves to defrost any frost buildup within the system, lncluding, in particular, on the refrigeration coils. The direction of air flow during the defrost cycle is shown by the arrows in Figure 3.
Another embodiment of the invention is sho~n in Figures 4 and 5. Display case 30 has an access opening 32 and an air conduit 36. The major difference between display case 30 and display case 2 is the absence of sloped inner wall 28. Otherwise both display cases operate in substantially the same manner.
The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are pre-sented merely as illustrative and not restrictive, with the scope of the invention being indicated by the attached claims rather thanthe foregoing description. All changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Patent No. 3,082,612 to Beckwith, which system draws ambient air into the main circulation path through ports located in the lower front panel of the refrigerated display case. Such ports are normally closed during the refrigeration cycle and are opened during the defrosting-cycle. The Beckwith et al.
'003 patent indicates that the concepts described in patents Nos. 3,082,612 and 3,403,525 did not prove to be practical .:
and hence were not commercially feasible.
Finally, a third type of ambient air defros~ing system is shown in U.S. Pat~nt No. 4,144,720 to Subera et al., which is assigned to the same assignee as the present applica-tion. In the foregoing patent application, an open frontrefrigerated display case having primary and secondary air conduits is disclosed. In this system, reversible fans are employed for reversing the direction of flow of air within the conduits and simulataneously drawing in air from outside of the display case.
Another system employing reversible fans for ambient air defrost is shown in U.S. Patent No. 4,026,121. This patent, however, refers to short-circulating the air flow between the primary and secondary air bands for the purpose of supplying warmer air to the primary band.
It has been recognized that an ambient air defrost operation can be incorporated into an open top refrigerated display case as disclosed in U.S. Patent No. 4,120,174 to - Johnston. The Johnston patent illustrates an open top case having a single air conduit extending around the c;ase.
During the refrigeration cycle, the air flows in a first direction and during the defrost cycle the direction of the air flow is reverse with ambient air being drawn into the conduit. The quantity of air flow during the defrost cycle ~ ~is greater than during refrigeration. The defrost air, after passing through the conduit, is expelled in a direction up and over the refrigerated case. It has been found during the development of the present inventlon, that with a defrost .
S~
~3 air flow pa-ttern such as disclosed in the Johnston paten-t a significant portion of the expelled air will fall back towards the access opening in the refrigerated case and reenter the air conduit at the other side of the access opening.
Similar to the open top display case of the above-identified patent to Johnston, there also are open front single air conduit cases which employ the same air defrost techniques as disclosed by the Johnston patent. During the defrost operation of such air defrost cases, the volume of the reverse air flow is relatively high and significantly greater than the air flow flow during the refrigeration cycle.
Such a greater air flow is utilized so as to minimize the time needed for the defrost operation. As shown in Figure 1, which illustrates this type of prior art display case, the higher air volume flow causes the warmer defrost air to re-enter the display case which potentially can damage the products in the case. In addition the greater air flow causing the cold air to flow upwardly can result in hitting the customer in the face with such cold air.
r.
SU~M~RY OF T~E INVENTION
An object of the present invention is to provide an improved ambient air defrost system within a single air conduit open front refrigerated display case.
Another object of the present invention is to provide an energy efficient open front refrigerated display case employing an improved ambient air defrost system in which the ambient air is drawn into the air conduit by re-versing the direction of flow of air through the conduit.
f~
A further object of the present invention is to provide an open front refrigerated display case having a single air conduit and a reversible fan arranged within the conduit for propelling air in a forward direction through the refrigeration coils during a refrigeration cycle and circulating air in a reverse direction so as to draw in ambient air from outside of the case during a defrost cycle and to prevent the defrost air when expelled from the conduit from being drawn back into the refrigerated case.
A still further object of the present invention is to provide an improved procedure for defrosting an open front refrigerated display case by the use of ambient air.
These objectives are achieved by the utilization of a refrigerated display case with a front access opening that is constructed in accordance with the present invention.
The display case is providedwith an approximatel~ U-shaped air conduit that extends around the display case and has openings at its opposite ends at opposite sides of the access opening of the display case. Arranged within the air conduit are the refrigeration coils and at least one reversible fan.
- In larger display cases, it is often necessary to use either two or three fans spaced along the longitudinal axis of the _ case in order to generate a sufficient force for circulating the air; in such a system, however, each fan preferable would be a reversible fan and operate in the same manner as disclosed herein in accordance wi-th the present invention.
The reversible fan arranged within the U-shaped air conduit is capable of either circulating in a first direction towards the refrigeration coils during a refrigeration -~3~'7~
cycle or when the case is switched into a defrost cycle circulating the air in a second, opposite, direction. For the sa~e of convenience herein, the first direction shall be referred to as the forward direction and the second, opposite, direction as the reverse direction. The openings in the ends of the air conduit are aligned so that during the refrigeration cycle, refrigerated air leaves a first of the openings in a path towards the second opening so as to form an alr curtain across the access opening in the display case. This air travelling across ~he access opening in the display enters the second opening in the air conduit and is drawn along the conduit back towards the fan thereby establish-ing a continuous refrigerated air band. When the display case is switched into a defrost cycle, th~ refrigeration coils are deactivated and the direction of air flow is re-versed. The volume of the air flow during defrost is lower than the volume during refrigeration. During such reverse air flow, the air leaves the air conduit through the second opening. The air leaving the conduit is cooler than the ambient air since it has passed over the refrigeration coils for defrosting them; this expelIed defrost air being some-what cooled, therefore, is denser than the ambient air.
The dense defrost air being propelled at a lower volume and hence slower speed will fall to the floor as it leaves the air conduit. Hence the defrost air falls away from the display case; i.e., towards the outside of the display case, thereby preventing portions of the defrost air from reentering the case and travelling across the access opening in the case ~ ,r~
7'~
and being drawn back into the air condui-t. With such an air flow pattern, the defrost air also will not hit the customer in the face with cold air. The area of the second opening can be constructed to help direct the defrost air flow away from the display case. Consequently, during the reverse flow of air no air curtain is established and hence ambient air from outside of the case is drawn in through the first opening in the air conduit. Such ambient air being warmer than the refrigerated air serves to defrost the refrigeration coils.
It is advantageous to avoid having the defrost air flow reenter the display case and also reenter the air conduit. While the ambient air as it passes over the evapora-tor coils expels heat to the coils and the air drops in temperature, the temperature of such air is still warmer than the temperature to which the products are refrigerated.
If the defrost air reenters the conduit then this will significantly slow down the defrost operation. In addition, if the defrost air contacts the products it will raise the temperature of the products. By causing the defrost air to fall away from the refrigerated case, the products are protected without detrimentally increasing the defrost time perlod .
As frost accumulates-on the evaporator coils during the refrigeration cycle, the conduit becomes blocked. Hence when the defrost cycle is initiated the ~uantity of air flow will be substantially less than the air flow during the refrigeFation cycle. As the defrost cycle continues and the _g_ __ _. . . .. .. .. . . . ___ .__._. .. _ ... ~_~
~ 7L~
frost is eliminated, the defrost air flow will rise back toward the level of the re~rigeration air flow, although not surpassing it.
In order to eliminate the buildup of condensation and frost on the grill structures mounted at the openings at the ends of the air conduit, it may be desirable to pro-vide some type of mechanism for generating heat in these areas. For this purpose, within each of the areas, tubes containing the liquid refrigerant used in the system can be provided. These tubes are connected to the line that carries the liquid refrigerant for the refrigeration coils.
Since the liquid refrigerant is warmer than the refrigerated air, the tubes provide a limited quantity of heat within each of the openings. The quantity of heat, however, is sufficient to help eliminate the condensation and the re-sulting buildup of frost.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a sectional side elevational view of - an open front refrigerated display case in accordance with the prior art, when the display case is operated during a ; defrost cycle with the air flow being relatively high.
Figures 2 and 3 are sectional side elevational views of one embodiment of an open front refrigerated display case in accordance with the present invention, with Figure 2 showing the air flow pattern during refrigeration and Figure 3 showing the pattern during defrost.
Figures 4 and 5 are views similar to Figures 2 and 3 respectively of another embodiment of the present invention.
~3~
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An open front refrigeratecl display case 2 construc-t-ed in accordance with the present invention is illustrated in Figure 2. The display case has top, bottom, rear and side walls along with a partial front ~all. All of these walls are appropriately insulated. Front wall 4 has an access opening 6. Positioned above bottom wall 8 are a plurality of shelves 10, 12 and 14. The spacing between shelf 10 and bottom wall 8 is large enough to enable the fans and if desired the refrigeration coils, which are described later herein, to be arranged within that location. Extending along the top wall, rear wall and bottom wall is an air conduit 16. Arranged within air conduit 16 is at least one fan 18.
While only one fan is illustrated, typically for refrigerated cases that are eight feet long, two fans are employed and for cases twelve feet long there are three fans. The number of fans merely depends on the length of the case and the sige of the fans but have no bearing upon the scope of the present lnvention. All the fans arranged within air conduit 16 are reversible fans capable of being driven for propelling air in either direction.
ir conduit 16 has openings 20 and 22 at both of its ends at the top of the refrigerated display case. A
directional control grill 24 is mounted across opening 20.
Grill 24 is preferable constructed so as to assist in direct-ing air leaving a:ir conduit 16 through opening 20 towards opening 22 on the opposite side of access opening 6 of the display case. At the opposite side of the display case across opening 22 there is only positioned a cover plate having a plurali-ty of openings. The cover plate arxanged across opening 22 helpsto diffuse the air emitted during defrost. Such air directing grill structure and cover plate are generally known ln the prior art. In addition to help-ing in controlling the direction of Elow of the air enteringand leaving openings 20 and 22, the grill and cover plate also protect the openings from various debrls, such as trash, keys and coins.
Refrigeration coils 26 are positioned within air conduit 16 at a location either adjacent to or above fan 18, such as shown in the figures. In a conven~ional manner, when the display case is operated in a refrigeration cycle, the air passing through refrigeration coil 26 is cooled, or refrigera-ted. The extent to which air is cooled depends on the use to which the display case is to be put. If the display case is to serve for holding frozen food, then the air must be sufficiently cooled so as to maintain the interior of the case below 32F. If, however, the display case is used for storage of non-frozen products, such as 20~ dairy products, then a termperature slightly in excess of - 32F can be maintained. The term refrigeration, however, as used herein is intended to cover both types of system.
- Turning now to the structural arrangement in the area of opening 22, as shown in Figures 2 and 3, the inner surface 28 of the top part of the lower portion of front wall 4 is sloped in a direction towards the outside of dis-play case 2. This sloped construction of surface 28 helps to direct air leaving conduit 16 through opening 22 during ~ t7~
a defrost operation in a direction away from the display case as shown by the arrows in Figure 3.
During the refrigeration cycle of operation of the display case, air is circulated through air conduit 16 by fan 18 in a forward direction towards and through refrigeration coils 26, which are activated for cooling.
The volume of air flow during refrigeration is between 1000 and 1400 cfm. The air is cooled wllen passing through refrig-eration coils 26. The cooled air then travels through tlle remaining portion of conduit 16. As the air reaches opening 20 in conduit 16, it is forced out through grill 24 in a direction towards opening 22. In this manner, a curtain of cooled air is established across access opening 6 of the display case. The cooled air serves to refrigerate the lS products in the display case and also separate the warmer ambient air outside of the display case from the cooler air inside of the display case.
The air emitted through grill structure 24 and traveling across the access opening is received into open-ing 22 in the air conduit. This air is then drawn back intoair conduit 16 by a suction force established by fan 18.
Thus, during the refrigeration cycle a continuous band of cooled air is circulated by fan 18 through the display case.
The direction of travel of such air along the air band is illustrated in Figure 2.
Turning now to the defrost cycle, the air flow during this cycle of operation is illùstrated in Figure 3O
In any one of different conventional manners, the display case can be thermostatically or otherwise controlled so as -to switch between the refrigeration cycle and the defrost cycle. By one such technique, the switching can occur when a cer-tain degree of frost bui.ldup is detected on the refrig-eration coils. Another possible alternative is at set time intervals to switch the operation of the display case from a refrigeration cycle to a def.rost cycle.
During the defrost cycle, the operation of fan 18 is reversèd so as to propel air in a reverse direction away from refrigeration coils 26. When the fan is operated in this mode, air passes along conduit 16 out through open-ing 22. The air upon exiting from opening 22 is diffused and falls to the floor outside of the.case. In addition, the lower portion of wall 4 at its upper end has sloped inner surface 28. As the air leaving conduit 16 during the defrost cycle passes along sloped wall 25, the path of air curves into an arc directed up and away from display case 2.
Thus, in this mode of operation, there is no air curtain established across the access opening of display case 2 and also no continuous air band established through the display case. The volume of air flow during the.defrost operation is between 800 and 1100 cfm and should be less than the air flow during refrigeration. If the air flow during defrost is increased to above 1600 cfm then a curtain of air will be es-tablished across access opening 6 during the defrost 25: operation.
As air is propelled out of conduit 16 through opening 22, a partial vacuum is estabiished within the air conduit so as to cause air to be sucked into the conduit through opening 20. Since there is no air curtain in ,, " - ~
7,. ~
existence across the top of the display case during the de-frost cycle, the air sucked into the conduit through open-ing 20 is drawn from the ambient air surrounding the display case. Since such ambient air is of a higher temperature than the refrigerated air during the refrigeration cycle, such ambient air serves to defrost any frost buildup within the system, lncluding, in particular, on the refrigeration coils. The direction of air flow during the defrost cycle is shown by the arrows in Figure 3.
Another embodiment of the invention is sho~n in Figures 4 and 5. Display case 30 has an access opening 32 and an air conduit 36. The major difference between display case 30 and display case 2 is the absence of sloped inner wall 28. Otherwise both display cases operate in substantially the same manner.
The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are pre-sented merely as illustrative and not restrictive, with the scope of the invention being indicated by the attached claims rather thanthe foregoing description. All changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (15)
- Claim 1 continued...
case comprising said second opening and the portion of said air conduit adjacent to said second opening which are con-structed such that air leaving said opening during a defrost cycle is directed away from said case. - 2. A display case according to claim 1 wherein said first opening within said air conduit serves as an air outlet during a refrigeration cycle and said second opening serves as a return air inlet during a refrigeration cycle, said first and second openings are aligned so that at least a substantial portion of air leaving said first opening during a refrigeration cycle is received within said second opening thereby enabling a continuous refrigerated air band to be established within said case during a refrigeration cycle.
- 3. A display case according to claim 2, wherein during a defrost cycle, said air circulating means serves to draw in ambient air surrounding said case into said air conduit through said first opening.
- 4. A display case according to claim 1 further comprising means for providing heat within said air conduit in the area of said second opening during a refrigeration cycle so as to limit the amount of condensation and frost buildup within the area of said second opening during such refrigeration cycle.
- 5. A display case according to claim 4 wherein said means for providing heat includes a plurality of tubes containing a liquid having a higher temperature than the air entering said second opening during a refrigeration cycle.
6. A display case according to claim 5 further comprising further heating means for providing heat within said air conduit in the area of said first opening during a refrigeration cycle - Claim 6 continued....
so as to limit the amount of condensation and frost buildup within the area of said first opening during such refrigeration cycle. - 7. A display case according to claim 6 wherein said further heating means includes a plurality of further tubes containing a liquid having a higher temperature than the air leaving said first opening during a refrigeration cycle.
- 8. A display case according to claim 7 wherein said liquid in all of said liquid containing tubes is liquid refrigerant that is also circulated through said refrigerating means.
9. A method for selectively operating an open front refrigerated display case in a refrigeration cycle and a defrost cycle, where the case includes a top, rear, front and bottom wall with an access opening in the front wall and a single air conduit extending along the top, rear and bottom walls, the air conduit having first and second openings at its opposite ends and each of the openings being located on opposite sides of the access opening; the method comprising the steps of: refrigerating air moving through the air conduit during a refrigeration cycle; circulating air within the air conduit in a forward direction during a refrigeration cycle; circulating air in a reverse direction during a defrost cycle; drawing in ambient air from outside of said display case through the first opening when air is circulated within the air conduit in the reverse direction; switching the operation of the display case between the refrigeration cycle and the defrost cycle and correspondingly causing the direction of circulation of air within the air conduit to be changed; and causing substantially all air leaving the air - Claim 9 continued...
conduit during substantially the entire defrost cycle to flow away from the case when such air is flowing in the reverse direction. - 10. A method according to claim 9 further comprising the step of drawing in ambient air surrounding the display case into the air conduit through the first opening during a deforst cycle.
- 11. A method according to claim 9 wherein the air flow volume during a defrost cycle is lower than the air flow volume during a refrigeration cycle.
- 12. A method according to claim 11 wherein the air flow volume during refrigeration is between 1000 and 1400 cfm and the air flow volume during defrost is between 800 and 1100 cfm.
- 13. A method according to claim 9 further comprising the step of drawing ambient air surrounding the display case into the air conduit through the first opening during a defrost cycle and wherein the air flow volume during the defrost cycle is lower than the air flow volume during a refrigeration cycle.
14. A display case according to claim 2, wherein: during a defrost cycle, said air circulating means serves to draw ambient air surround said case into said air conduit through said first opening; and said second opening and the portion of said air conduit adjacent to said second opening are con-structed such that air leaving said second opening during a defrost cycle is directed away from said case, and further comprising means for providing heat within said air conduit in the area of said opening during a refrigeration cycle so as - Claim 14 continued....
to limit the amount of condensation and frost buildup within the area of said second opening during such refrigeration cycle. - 15. A display case according to claim 1, wherein said air circulating means circulates an air flow volume during the defrost cycle which is lower than the air flow volume during a refrigeration cycle, and wherein said air circulation means and said means for causing substantially all air leaving said air conduit during substantially the entire defrost cycle to flow away from said case cooperate with one another to prevent such air from reentering said case during substantially the entire defrost cycle.
1. A display case for the storage of refrigerated products therein and having an access opening in its front wall for enabling the refrigerated products to be removed, said display case being selectively operative in a refrigeration cycle and a defrost cycle, said case comprising: a single air conduit extending along said display case, said air conduit being approximately U-shaped and having first and second openings at its opposite ends and each of said openings being located at one side of said access opening; means for re-frigerating air moving through said conduit during a refrigeration cycle, said means for refrigerating being arranged within said air conduit; air circulating means arranged within said air conduit, said air circulating means circulating air within said air conduit in a forward direction during a refrigeration cycle and circulating air in a reverse direction during a defrost cycle, and said air circulating means drawing in ambient air from outside of said display case through said first opening when said air circulating means circulates air within said air conduit in the reverse direction; means for switching the operation of said display case between a refrigeration cycle and a defrost cycle and correspondingly causing said air circulating means to change the direction of circulation of air within said air conduit; and means for caus-ing substantially all air leaving said air conduit during sub-stantially the entire defrost cycle to flow away from said case when such air is flowing in said reverse direction so that such air is prevented from reentering said air conduit, said means for causing substantially all air to flow away from said
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11757180A | 1980-02-01 | 1980-02-01 | |
| US117,571 | 1980-02-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1139574A true CA1139574A (en) | 1983-01-18 |
Family
ID=22373620
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000367125A Expired CA1139574A (en) | 1980-02-01 | 1980-12-18 | Single air conduit refrigerated display case having ambient air defrost |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS56110865A (en) |
| CA (1) | CA1139574A (en) |
| DE (1) | DE3101372A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3505341A1 (en) * | 1984-02-17 | 1985-08-22 | Linde Ag, 6200 Wiesbaden | Refrigerated shelf unit |
-
1980
- 1980-12-18 CA CA000367125A patent/CA1139574A/en not_active Expired
-
1981
- 1981-01-14 JP JP331081A patent/JPS56110865A/en active Pending
- 1981-01-17 DE DE19813101372 patent/DE3101372A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE3101372A1 (en) | 1981-12-24 |
| JPS56110865A (en) | 1981-09-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5675983A (en) | Synergistic refrigerated display case | |
| US4776182A (en) | Circulating air refrigerator and power module for same | |
| US3107502A (en) | Air circuit means for combined freezer and refrigerator apparatus | |
| US3393530A (en) | Radiant defrost panel for refrigerator | |
| US3992171A (en) | Refrigerator freezer forced air system | |
| CA1111668A (en) | Refrigeration system using air defrost | |
| US3104533A (en) | Refrigerating apparatus | |
| US3659429A (en) | Refrigerator-freezer with fast chill arrangement | |
| US3232071A (en) | Air flow control for use in refrigeration apparatus | |
| GB2091402A (en) | Refrigerated display case and method of defrosting same | |
| US3421338A (en) | Self-defrosting refrigerators | |
| US4449374A (en) | Combination hot gas and air defrost refrigerated display case | |
| CA1138666A (en) | Multiband open front refrigerated case with air defrost | |
| US4514988A (en) | Refrigerated display case having ambient air defrost | |
| US4347710A (en) | Glass door merchandizer with tertiary air band | |
| US4295340A (en) | Refrigerated display case having ambient air defrost | |
| US4304098A (en) | Method and apparatus for defrosting cooling elements in an open type freezer chest | |
| US4457139A (en) | Refrigerated display case having ambient air defrost | |
| US2994209A (en) | Frostless refrigerator | |
| US4308726A (en) | Open top refrigerated display case with storage section | |
| USRE31909E (en) | Refrigerated display case having ambient air defrost | |
| US3633375A (en) | Refrigerator cooling system design | |
| US4338792A (en) | Refrigerated merchandiser display case with defrost device | |
| CA1139574A (en) | Single air conduit refrigerated display case having ambient air defrost | |
| US4341082A (en) | Open top refrigerated display case having ambient air defrost |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |